Measuring device for residual stress of deployable and non-deployable curved surface composite material structure

Abstract

The invention relates to a device for measuring residual stress of an expandable and non-expandable curved surface composite material structure. The device comprises a laser generation module, a moire interference module, a drilling module, a workpiece clamping module, an image acquisition module and a moire interference module, the laser generation module is used for emitting laser to the moire interference module; the moire interference module comprises a collimating lens module, a double-hole light barrier, a total reflection mirror and a reflection mirror with an adjustable inclination angle; the collimating lens module is used for receiving the laser and dividing the laser into a plurality of directions; a total reflection mirror and a reflection mirror are respectively arranged in each light splitting direction of the collimating lens module and are used for reflecting split light generated by the collimating lens module to a workpiece; the double-hole light barrier is used for selecting split light in one direction to irradiate a workpiece; the inclination angle adjustment of the reflector is used for adjusting the angle of incident light on the workpiece. Compared with the prior art, the device has the advantages of convenience in adjustment, high measurement precision and the like.

Description

Technical Field

[0001] The invention relates to the technical field of residual stress measurement of composite materials, and in particular to a residual stress measurement device for composite material structures with developable and non-developable curved surfaces. Background Art

[0002] In modern aerospace satellites, aircraft, ships, high-performance cars and other fields, the design and manufacture of radar antenna covers, wing shells, ship internal components, sports car spoilers, etc. often involve a large number of expandable and non-expandable complex surfaces. The Gaussian curvature of expandable surfaces is zero, with good flexibility and adaptability. Its structure is simple and usually has strong anti-bending and anti-twisting capabilities, such as hull internal components and outfitting parts. The Gaussian curvature of non-expandable surfaces is not zero, and it is more likely to generate stress during production and manufacturing, but its special curvature design gives it good aerodynamics and mechanical properties. Non-expandable surfaces are widely used in aerospace, aircraft, high-performance sports cars and other fields. These streamlined or spherical surface designs are not only for aesthetics, but more based on the needs of aerodynamics and structural strength. Carbon fiber resin composite components with expandable and non-expandable surfaces are particularly widely used because of their advantages such as light weight, high strength, good aerodynamics and mechanical properties, and residual stress is an important factor affecting their reliability, service life and mechanical properties. Residual stress detection can provide an important reference for improving manufacturing processes and predicting product life. Correctly measuring and characterizing residual stresses in composite components with developable and non-developable surfaces has always been a complex problem.

[0003] The unidirectional plies of carbon fiber reinforced composite materials are composed of fibers and matrix, and are uneven in microstructure. In addition to the unevenness within the plies, laminated composite materials are also uneven along the thickness direction due to the different ply materials and ply directions, showing layered properties. The streamlined design of the expandable or non-expandable curved surface makes the residual stress inside the composite component even more uneven, and there are huge differences in stress gradients, making it difficult or even impossible to obtain an accurate solution. Moreover, the influence of the process and various parameters of this curved surface during the processing and manufacturing process makes it very complicated and difficult to calculate the residual stress of composite materials and their structures. At present, more experimental tests are used to determine the magnitude and direction of the residual stress of the composite structure with complex curved surfaces.

[0004] There are many methods for testing residual stress. According to whether the object to be tested is damaged, it can be divided into two categories: destructive testing method and non-destructive testing method. Drilling method, stripping method, grooving method and layer shifting method are all destructive testing methods; X-ray diffraction method, neutron method, ultrasonic method, electromagnetic method, etc. are all non-destructive testing methods. Among them, drilling method is one of the widely used residual stress testing methods. It is simple to operate, mature in technology, and has little damage to components. The most common method is to use resistance strain rosettes combined with drilling method and layer shifting method. ASTM in the United States has also specially formulated standards for this residual stress testing method. However, since the resistance strain rosette only tests one strain in three directions, and it is an average value, and the laminated structure of the composite material with complex curved surface makes its residual stress different in size and direction in a very small area, the traditional resistance strain rosette test of the residual stress of the curved composite material has a large error.

[0005] The traditional strain gauge drilling method has insurmountable defects in releasing strain during the drilling process, which limits the measurement accuracy of this method. In recent years, some optical measurement methods, such as holography, electronic speckle, electronic dislocation speckle, and moiré method, have gradually been combined with the drilling method to improve the measurement accuracy to a certain extent. The traditional moiré interferometer usually projects two beams of coherent light onto the specimen grid at a fixed incident angle to produce interference fringes. The incident angle will affect the spacing of the interference fringes. For different measurement objects and measurement ranges, the required fringe spacing is different. Large spacing is suitable for measuring large deformations, while small spacing is suitable for measuring small deformations. If the fringes are too dense or too sparse, the measurement accuracy may be affected. For the stress gradients of expandable and non-expandable curved composite structures, which are very different, the traditional moiré interferometry technology cannot flexibly adapt to the stress gradient differences of curved composite specimens at a fixed incident angle.

[0006] To this end, for expandable and non-expandable curved surface composite material components, the present invention has designed a residual stress measurement system for expandable and non-expandable curved surface composite material components based on the incremental drilling method combined with the three-directional moiré interference technology. It is equipped with a special-shaped flexible universal fixture experimental platform, which can measure expandable and non-expandable curved surfaces or carbon fiber composite material components with complex geometric structures. It has a wide range of applications and strong versatility. The present invention can conveniently adjust the incident angle of the light field and change the frequency of the spatial virtual grating to achieve frequency conversion, that is, the incident angle can be controlled to obtain interference fringes with different spacings to adapt to the huge differences in stress gradients of expandable and non-expandable curved surface composite components, thereby improving the accuracy and flexibility of the measurement. The optical path of the laser 1-filter plate module 2-spatial filter 3 is arranged on the same guide rail, which greatly improves the efficiency and convenience of adjusting the coaxial alignment of the optical axis.

[0007] For example, the invention with publication number CN103033297A discloses an optical non-destructive testing instrument, which tests the residual stress of the specimen along the depth by using the moiré interference technology. However, the patent does not involve a test fixture for composite material components with special curved surfaces or complex geometric structures, and the optical path module is not designed with a slide rail base, which makes the operation during the debugging of the optical axis more cumbersome and inconvenient.

[0008] The invention patent CN 117053964A discloses a method for measuring residual stress of fiber reinforced composite materials based on incremental drilling method. The invention uses resistance strain gauges to drill holes layer by layer to collect residual stress of fiber reinforced composite materials. However, the invention has the disadvantage that it only uses drilling method and does not involve moiré interference technology. The strain average value is taken over a relatively large area of ​​the strain gauge, which results in a certain error.

[0009] However, the above prior art has the following problems:

[0010] 1. It is difficult to correctly measure and characterize the residual stress of composite materials with complex curved surfaces. Similar traditional residual stress measurement devices are generally only suitable for common geometric structure specimens, which have certain limitations and poor versatility. There is a lack of residual stress measurement devices that can be applied to developable and non-developable surfaces with different curvatures or composite components with complex geometric structures.

[0011] 2. The traditional moiré interferometry combined with drilling method to measure residual stress is complicated and difficult to control in terms of debugging operations such as coaxial centering of the optical axis and parallelism of the light beam before testing, which is not conducive to batch testing and has low test efficiency.

[0012] 3. Traditional moire interferometry technology generally cannot achieve frequency conversion of the incident light field, or the frequency conversion operation is cumbersome and complicated. Traditional moire interferometry technology cannot flexibly adapt to the stress gradient differences of curved composite specimens at a fixed incident angle.

[0013] 4. The traditional resistance strain gauge drilling method only measures one strain in three directions, and it is an average value. However, residual stress is inherently random, and its size and direction are likely to change in a very small area, so this method inevitably has errors. Especially for some complex curved carbon fiber composite materials, the residual stress of its components may vary greatly in a very small area, so it is inevitable to replace it with the average strain value over a relatively large area, which means that there will be errors. Summary of the invention

[0014] The purpose of the present invention is to provide a residual stress measuring device for expandable and non-expandable curved composite material structures in order to overcome the defects of the prior art that the optical axis coaxiality and light beam parallelism debugging operations before testing are cumbersome and the frequency conversion of the incident light field is difficult to adjust.

[0015] The purpose of the present invention can be achieved by the following technical solutions:

[0016] A residual stress measuring device for expandable and non-expandable curved surface composite material structures, comprising a laser generating module, a moiré interference module, a drilling module, a workpiece clamping module, an image acquisition module and a moiré interference module; the laser generating module is used to emit laser to the moiré interference module; the drilling module is used to drill holes in the workpiece; the workpiece clamping module is used to clamp the workpiece; the image acquisition module is used to obtain a fringe pattern on the workpiece;

[0017] The moiré interference module includes a collimating lens module, a double-aperture light-blocking plate, a total reflector and a reflector with adjustable inclination angle; the collimating lens module is used to receive laser light and separate the laser light into multiple directions; a total reflector and a reflector are respectively arranged in each splitting direction of the collimating lens module, so as to reflect the split light generated by the collimating lens module onto the workpiece; the double-aperture light-blocking plate is rotatably arranged between the collimating lens module and the total reflector, so as to select the split light in one direction to irradiate the workpiece; the inclination angle adjustment of the reflector is used to adjust the angle of the incident light on the workpiece.

[0018] Preferably, the collimating lens module comprises a collimating lens base, a base adjusting bolt and a collimating lens;

[0019] The collimating lens base includes a first fixing layer and a second fixing layer, the first fixing layer and the second fixing layer are connected by a base adjusting bolt, the adjusting bolt is used to adjust the inclination angle of the first fixing layer, the first fixing layer is provided with a lens mounting hole matching the collimating lens, and the collimating lens is installed in the lens mounting hole; the second fixing layer is provided with a plurality of first-level light-transmitting holes that are centrally symmetrically distributed.

[0020] Preferably, the double-hole light-blocking plate can be rotatably fixed on a side of the second fixed layer away from the first fixed layer, and the double-hole light-blocking plate is provided with two symmetrical secondary light-transmitting holes, and the secondary light-transmitting holes are located directly below the primary light-transmitting holes.

[0021] Preferably, the collimating lens module further comprises an upper plate base, and the upper plate base is provided with third-level light-transmitting holes having the same number as the first-level light-transmitting holes;

[0022] The number of the total reflection mirror and the reflector is the same as the number of the primary light-transmitting holes. The total reflection mirror and the reflector are both fixed on the upper plate base. The total reflection mirror is located directly below the primary light-transmitting hole and is used to emit the split light passing through the secondary light-transmitting hole to the reflector. The reflector is located directly above the tertiary light-transmitting hole. The workpiece clamping module is located on the side of the upper plate base away from the reflector. The reflector is used to reflect the split light and irradiate it onto the workpiece through the tertiary light-transmitting hole.

[0023] Preferably, the reflector includes a fixing plate, an adjusting plate, a reflective lens and a lens adjusting bolt;

[0024] The fixing plate is fixed on the upper plate base, one end of the adjusting plate is provided with an inclined portion, the reflecting lens is fixed on the inclined portion, and the end of the adjusting plate opposite to the inclined portion is adjustably mounted on the fixing plate through a lens adjusting bolt, and the lens adjusting bolt is used to adjust the angle of incident light on the workpiece.

[0025] Preferably, a framing total reflector is installed on a side of the upper plate base away from the collimating lens module, and the framing total reflector is located directly above the workpiece and is used to reflect the stripes on the workpiece to the image acquisition module.

[0026] Preferably, the laser generating module comprises a laser module, a filter module, a spatial filter module and a spatial adjustment structure;

[0027] The laser module, filter module and spatial filter module are fixed on the spatial adjustment structure, and the filter module and spatial filter module are used to filter stray light during laser propagation; the spatial adjustment structure is used to adjust the heights of the laser module, filter module and spatial filter module respectively.

[0028] Preferably, the workpiece clamping module includes a workbench and two clamping arms. A plurality of array-arranged clamp floating pins are provided on the opposite side of the clamping arm for adapting to the shape of the workpiece. A floating pin locking switch is also provided on the clamping arm for fixing the clamp floating pin. A spacing adjustment structure is installed on the workbench for adjusting the spacing between the two clamping arms. The workbench is used to adjust the position of the clamping arm on the horizontal plane.

[0029] Preferably, the drilling module comprises a drill bit, a horizontal stepping motor and a vertical stepping motor;

[0030] The output shaft of the vertical stepper motor is connected to the drill bit for adjusting the longitudinal position of the drill bit, and the output shaft of the horizontal stepper motor is connected to the horizontal stepper motor for adjusting the lateral position of the drill bit.

[0031] Preferably, the image acquisition module includes a CCD industrial camera and a telescopic structure, the CCD industrial camera is fixed on the telescopic structure, the telescopic structure is used to adjust the height of the CCD industrial camera, the CCD industrial camera is used to obtain the stripe pattern on the workpiece, the CCD industrial camera is connected to a computer, and the obtained stripe pattern is uploaded to the computer.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) This solution uses a collimating lens module to separate the laser into multiple directions after it is diverged. Each time, a double-hole light-blocking plate is used to select a direction of split light to irradiate the workpiece. By rotating the double-hole light-blocking plate, the split light direction irradiated on the workpiece is adjusted, and multiple strain components at any point on the workpiece can be obtained, and the corresponding stress can be calculated, thereby reducing the measurement error caused by the traditional method of taking the average strain value over a large area and improving the measurement accuracy. In addition, by adjusting the inclination angle of the reflector, the frequency conversion of the incident light field on the workpiece is achieved, the density of the interference fringe spacing is controlled, and the stress gradient differences of expandable and non-expandable curved composite components are adapted, thereby improving the flexibility and accuracy of the measurement.

[0034] (2) In this scheme, the laser module, the filter module and the spatial filter module are fixed on the spatial adjustment structure in sequence, and the positions of the laser module, the filter module and the spatial filter module can be flexibly adjusted through the spatial adjustment structure. The structure is simple, and the coaxial centering of the optical axis and the debugging of the parallel light field during the test are simple and convenient. In addition, the combination of the filter module and the spatial filter is used to filter out impurities at the edge of the light field, making the light field more uniform and pure, thereby improving the contrast of the stripes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of the measuring device provided by the present invention;

[0036] Figure 2 A schematic diagram of the structure of the laser module provided by the present invention;

[0037] Figure 3 A schematic diagram of the structure of the filter module provided by the present invention;

[0038] Figure 4 A schematic diagram of the structure of the spatial filtering module provided by the present invention;

[0039] Figure 5 A schematic diagram of the structure of the spatial filter provided by the present invention;

[0040] Figure 6 A schematic diagram of the structure of the connection between the optical path component fixing bracket and the base guide rail provided by the present invention;

[0041] Figure 7 A schematic structural diagram of the upper plate optical path assembly provided by the present invention from a first viewing angle;

[0042] Figure 8 A schematic diagram of the structure of the upper plate optical path assembly provided by the present invention from a second viewing angle;

[0043] Fig. 9 A schematic diagram of the structure of a double-hole optical disc provided by the present invention;

[0044] Fig.10A schematic diagram of the structure of the drilling machine provided by the present invention;

[0045] Fig.11 A schematic diagram of the structure of the special-shaped flexible universal fixture experimental platform provided by the present invention;

[0046] Fig.12 A schematic diagram of the structure of a CCD image acquisition device provided by the present invention;

[0047] Fig.13 A schematic diagram of the optical path of the moiré interferometry system provided by the present invention;

[0048] Fig.14 A principle flow chart of the moiré interferometry system provided by the present invention;

[0049] In the figure: 1. laser module, 2. filter module, 3. spatial filter module, 4. upper plate optical path assembly, 5. drilling machine, 6. special-shaped flexible universal fixture experimental platform, 7. CCD image acquisition instrument, 8. base rail, 9. drilling platform base, 10. workpiece, 14. grating, 15. computer; 11. laser, 12. optical path component fixing bracket, 111. laser transmitter, 112. base adjustment bolt; 21. filter structure, 211, filter plate, 212, filter hole, 213, clamping plate, 214, clamping screw, 215, U-shaped fixing seat; 31, spatial filter structure, 311, spatial filter, 312, high-power objective lens, 313, first adjusting bolt, 314, second adjusting bolt, 315, distance adjusting bolt, 316, concave fixing seat; 3111, handle, 3112, pinhole; 41, large flat total reflector, 411, large flat total reflector lens , 412, adjusting screw, 42, collimating lens, 421, collimating lens base, 422, base adjusting bolt, 423, straight lens, 43, double-hole light blocking disc, 431, secondary light transmission hole, 44, small full-reflection mirror, 45, reflector, 451, reflective lens, 452, adjusting bolt, 46, upper disc base, 461, rectangular through hole, 47, small plane full-reflection mirror, 471, small plane full-reflection lens, 472, first adjusting bolt , 51. Drill bit, 52. First stepper motor, 53. Second stepper motor, 54. Second adjusting bolt, 61. Floating needle of clamp, 62. Floating needle locking switch, 63. Jaw opening control handle, 64. Screw, 65. Workbench, 66. First fine-tuning bolt, 67. Second fine-tuning bolt, 71. CCD industrial camera, 72. Telescopic column, 73. Fixed bracket, 74. Limit screw, 75. Magnetic base, 76. Fastening screw. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0053] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0054] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0055] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0056] Example 1

[0057] like Figure 1As shown, this embodiment provides a residual stress measurement device for expandable and non-expandable curved surface composite material structures, including a laser generating module, a moiré interference module, a drilling module, a workpiece clamping module, an image acquisition module and a moiré interference module; the laser generating module is used to emit laser to the moiré interference module; the drilling module is used to drill holes in the workpiece; the workpiece clamping module is used to clamp the workpiece; the image acquisition module is used to obtain the fringe pattern on the workpiece;

[0058] The moiré interference module includes a collimating lens module, a double-hole light-blocking plate, a total reflector and a reflector with adjustable inclination angle; the collimating lens module is used to receive laser and separate the laser into multiple directions; a total reflector and a reflector are respectively arranged in each splitting direction of the collimating lens module, which are used to reflect the split light generated by the collimating lens module onto the workpiece; the double-hole light-blocking plate is rotatably arranged between the collimating lens module and the total reflector, which is used to select the split light in one direction to irradiate the workpiece; the inclination adjustment of the reflector is used to adjust the angle of the incident light on the workpiece.

[0059] Working principle: The laser generating module emits laser to the moiré interference module, and the collimating lens module diverges and separates the laser into light fields in multiple directions. The light fields in each direction are sequentially irradiated onto the workpiece through the total reflector and the reflector to form stripes. The double-hole light blocking plate set between the collimating lens module and the total reflector selects a direction of split light to pass through and blocks the split light in other directions. Only one direction of split light is irradiated onto the workpiece at a time and forms stripes. The drilling module cooperates with the workpiece clamping module to drill holes on the workpiece, and the image acquisition module is used to obtain the stripe images on the workpiece before and after drilling. By comparing the stripe images before and after drilling, the residual stress of the workpiece before drilling is obtained. The inclination of the reflector is adjusted to change the stripe spacing on the workpiece, and it is adjusted according to the measurement requirements and strain range of the workpiece.

[0060] The laser is diverged and separated into multiple directions by a collimating lens module. Each time, a split beam in one direction is selected through a double-hole light-blocking plate to irradiate the workpiece. The split beam direction irradiated on the workpiece is adjusted by rotating the double-hole light-blocking plate, so that multiple strain components at any point of the workpiece can be obtained, and the corresponding stress can be calculated, thereby reducing the measurement error caused by the traditional method of taking the average strain value over a large area and improving the measurement accuracy. In addition, by adjusting the inclination of the reflector, the frequency conversion of the incident light field on the workpiece is achieved, the density of the interference fringe spacing is controlled, and the stress gradient differences of expandable and non-expandable curved composite components are adapted to improve the flexibility and accuracy of the measurement.

[0061] Preferred implementation mode, as Figure 7 and Figure 8 As shown, the collimating lens module 42 includes a collimating lens base 421, a base adjusting bolt 422 and a collimating lens 423;

[0062] The collimating lens base 421 includes a first fixing layer and a second fixing layer, which are connected by a base adjusting bolt 422. The adjusting bolt 422 is used to adjust the inclination angle of the first fixing layer. The first fixing layer is provided with a lens mounting hole that matches the collimating lens 423, and the collimating lens 423 is installed in the lens mounting hole; the second fixing layer is provided with a plurality of first-level light-transmitting holes that are centrally symmetrically distributed.

[0063] The double-hole light-blocking plate 43 can be rotatably fixed on a side of the second fixed layer away from the first fixed layer. The double-hole light-blocking plate 43 is provided with two symmetrical secondary light-transmitting holes, which are located directly below the primary light-transmitting holes.

[0064] Specifically, the collimating lens module 42 further includes an upper plate base 46, and the upper plate base 46 is provided with third-level light-transmitting holes having the same number as the first-level light-transmitting holes;

[0065] The number of total reflection mirrors and reflective mirrors is the same as the number of primary light-transmitting holes. Both the total reflection mirrors and reflective mirrors are fixed on the upper plate base 46. The total reflection mirror is located directly below the primary light-transmitting hole and is used to emit the split light passing through the secondary light-transmitting hole to the reflective mirror. The reflective mirror is located directly above the tertiary light-transmitting hole. The workpiece clamping module is located on the side of the upper plate base 46 away from the reflective mirror. The reflective mirror is used to reflect the split light and irradiate it onto the workpiece through the tertiary light-transmitting hole.

[0066] Further, the reflector includes a fixing plate, an adjusting plate, a reflector lens 451 and a lens adjusting bolt 452;

[0067] The fixing plate is fixed on the upper plate base 46, one end of the adjustment plate is provided with an inclined portion, the reflecting lens 451 is fixed on the inclined portion, and the end of the adjustment plate opposite to the inclined portion can be adjustably mounted on the fixing plate through a lens adjusting bolt 452, and the lens adjusting bolt 452 is used to adjust the angle of incident light on the workpiece.

[0068] A framing total reflector is installed on one side of the upper plate base 46 away from the collimating lens module 42 . The framing total reflector is located directly above the workpiece and is used to reflect the stripes on the workpiece to the image acquisition module.

[0069] Preferred implementation mode, as Figures 2 to 6 As shown, the laser generating module includes a laser module 1, a filter module 2, a spatial filter module 3 and a spatial adjustment structure;

[0070] The laser module 1, the filter module 2 and the spatial filter module 3 are fixed on the spatial adjustment structure. The filter module 2 and the spatial filter module 3 are used to filter stray light during laser propagation. The spatial adjustment structure is used to adjust the heights of the laser module 1, the filter module 2 and the spatial filter module 3 respectively.

[0071] The laser module, filter module and spatial filter module are fixed on the spatial adjustment structure in sequence, and the positions of the laser module, filter module and spatial filter module can be flexibly adjusted through the spatial adjustment structure. The structure is simple, and the coaxial centering of the optical axis and the debugging of the parallel light field during the test are simple and convenient. In addition, the combination of the filter module and the spatial filter is used to filter out impurities at the edge of the light field, making the light field more uniform and pure, thereby improving the contrast of the stripes.

[0072] Preferred implementation mode, as Fig.11 As shown, the workpiece clamping module includes a workbench 65 and two clamping arms. A plurality of clamp floating pins 61 arranged in an array are provided on the opposite side of the clamping arm for adapting to the shape of the workpiece 10. A floating pin locking switch 62 is also provided on the clamping arm for fixing the clamp floating pin 61. A spacing adjustment structure is installed on the workbench 65 for adjusting the spacing between the two clamping arms. The workbench 65 is used to adjust the position of the clamping arm on the horizontal plane.

[0073] By arranging a fixture floating needle 61 on the opposite side of the clamping arm to form a flexible clamping arm, the fixture floating needle 61 on the clamping arm can adaptively change according to the structure of the workpiece 10, so that the clamping arm can clamp irregularly shaped workpieces 10, thereby improving the testing and use range of the device.

[0074] Among them, Fig.10 As shown, the drilling module includes a drill bit 51, a horizontal stepping motor 52 and a vertical stepping motor 53;

[0075] The output shaft of the vertical stepper motor 53 is connected to the drill bit 51 for adjusting the longitudinal position of the drill bit 51 , and the output shaft of the horizontal stepper motor 52 is connected to the horizontal stepper motor 52 for adjusting the lateral position of the drill bit 51 .

[0076] Specifically, Fig.12 As shown, the image acquisition module includes a CCD industrial camera 71 and a telescopic structure. The CCD industrial camera 71 is fixed on the telescopic structure. The telescopic structure is used to adjust the height of the CCD industrial camera 71. The CCD industrial camera 71 is used to obtain the stripe pattern on the workpiece 10. The CCD industrial camera 71 is connected to a computer and uploads the obtained stripe pattern to the computer.

[0077] In combination with the above preferred implementation, this embodiment provides a more specific implementation, such as Figures 1 to 14As shown, a residual stress measuring device for expandable and non-expandable curved composite material components based on three-way moiré interference of incremental drilling method includes: laser module 1, filter module 2, spatial filter module 3, large plane total reflection mirror 41, collimating lens 42, double-hole light blocking disk 43, six small total reflection mirrors 44, six reflectors 45, upper disk base 46, small plane total reflection mirror 47, drilling machine 5, special-shaped flexible universal fixture experimental platform 6, CCD image acquisition instrument 7, base rail 8, drilling platform base 9 and computer. The whole system device is placed on an optical seismic isolation platform for testing.

[0078] The laser module 1 , the filter module 2 and the spatial filter module 3 are installed on the same base rail 8 , and the CCD image acquisition device 7 is placed right in front of the small planar total reflective mirror 47 .

[0079] The laser module 1 includes a laser 11 and an optical path component fixing bracket 12. The laser 11 and the optical path component fixing bracket 12 are connected by a stud. The laser 11 includes: a laser emitter 111 and a base adjustment bolt 112. The base adjustment bolt 112 can be used to fine-tune the angle of the laser emitter 111.

[0080] The filter module 2 includes a filter structure 21, which includes a filter plate 211 with a filter hole 212, a clamping plate 213, two clamping screws 214, a U-shaped fixing seat 215 and a base fixing stud. The filter structure 21 and the optical path component fixing bracket 12 are connected through the base fixing stud. One side of the filter plate 211 is attached to the U-shaped fixing seat 215, and the other side is attached to the clamping plate 213. The clamping plate is supported by two clamping screws 214 to fix the filter plate 211. A tiny filter hole 212 is set in the middle of the filter plate 211, and the laser passes through this filter hole 212 to filter stray light in the laser propagation path.

[0081] The spatial filter module 3 includes a spatial filter structure 31 and an optical path component fixing bracket 12. The spatial filter structure 31 includes: a spatial filter 311, a high-power objective lens 312, a first adjustment bolt 313, a second adjustment bolt 314, a distance adjustment bolt 315 and a concave fixing seat 316. The laser 11 emits laser light, which is filtered through the filter light hole 212 in the laser propagation path, and then passes through the spatial filter module 3 to filter out impurities at the edge of the light field.

[0082] The handle 3111 and the pinhole 3112 can be disassembled by holding the handle 3111. The square housing of the spatial filter is made of iron, the head ends of the two adjusting bolts are threaded, and the tail ends are made of magnetic materials. The spatial filter 311 is connected by the magnetic attraction of the tail ends of the two adjusting bolts, and the first adjusting bolt 313 can adjust the spatial filter 311 to move left and right, and the second adjusting bolt 314 can adjust the spatial filter 311 to move up and down. The distance adjustment bolt 315 can adjust the distance between the high-power objective lens 312 and the spatial filter 311.

[0083] Among them, the filter module 21 and the spatial filter module 3 are both slidably mounted on the base guide rail 8 through the optical path component fixing bracket 12. The optical path component fixing bracket 12 is a retractable rod at both ends, and a tightening screw is set between the two end rods to adjust the length of the optical path component fixing bracket 12.

[0084] A large plane total reflection mirror 41 is arranged between the spatial filter module 3 and the collimating lens module, and the large plane total reflection mirror 41 comprises a large plane total reflection lens 411 and an adjusting screw 412. The large plane total reflection mirror 41 is adjusted to form an angle of 45° with the horizontal plane by adjusting the screw 412. The filtered light field is projected onto the large plane total reflection mirror 41 to reflect the light field to the collimating lens 42.

[0085] The collimating lens 42 includes a symmetrical collimating lens base 421 with six square holes, two base adjustment bolts 422, and a collimating lens sheet 423. The light field is transformed into a uniform collimated light field by passing through the collimating lens sheet 423. The light field then passes through the six symmetrical square holes of the collimating lens base 421 to obtain six collimated light fields.

[0086] Six collimated light fields are projected onto the double-hole blocking optical disc 43, and four light fields are blocked, with only two symmetrical beams of light passing through the secondary light-transmitting hole 431. The six regional light fields symmetrically form three pairs of light field combinations, corresponding to the measurement of the x-field, y-field and 45° direction light fields respectively. The double-hole blocking optical disc 43 can rotate around the center. If the light field in the x-axis direction needs to be measured, the double-hole blocking optical disc 43 is rotated until the double holes 431 are consistent with the x-axis direction. At this time, the double-hole blocking optical disc 43 blocks the light fields in the y-axis and 45° directions, and only allows the two symmetrical square hole light fields in the x-axis direction to pass, that is, the light field corresponds to the measurement of the x-field at this time. Similarly, the light fields in the y-axis and 45° directions can be measured.

[0087] The small total reflection mirror 44 is embedded in its inclined fixed base. The three-directional moiré interference upper plate optical path assembly 4 is provided with six small total reflection mirrors, which are arranged symmetrically in pairs and installed directly below the six square holes of the collimating lens base 421, and the six small total reflection mirrors are arranged one by one corresponding to the six square holes.

[0088] The reflector 45 is mounted on the upper plate base 46. The upper plate base 46 is symmetrically provided with six rectangular through holes 461. The six through holes are arranged in a one-to-one correspondence with the six reflectors 45. The six reflectors 45 correspond to the upper plate base 46. The light field passes through the collimating lens module 42, then passes through the double-hole blocking disk 43, and is reflected to the reflector 45 by the small total reflection mirror 44. After being reflected by the two symmetrical reflectors 45, the light field passes through the rectangular through hole 461 of the upper plate base. The two light fields are projected onto the grating 14 of the specimen at a certain incident angle to generate interference.

[0089] The reflector 45 includes a reflector lens 451 and two lens adjustment bolts 452. The lens adjustment bolts 452 can be used to fine-tune the inclination angle of the reflector 45. That is, the incident angles of the two light fields projected onto the grating 14 can be adjusted. When two beams of coherent light are incident on the specimen grating at different angles, spatial virtual gratings of different frequencies will be formed on the surface of the specimen. The angle of the incident light can be adjusted by using this changing frequency (i.e., frequency conversion) to control the spacing of interference fringes, thereby measuring displacements and strains of different sizes to adapt to the huge differences in stress gradients of expandable and non-expandable curved composite specimens. The upper plate optical path assembly 4 is provided with six reflectors 45, which are fixed to the upper plate base 46 by bolts and arranged one-to-one with the six small total reflection mirrors 44.

[0090] The facet total reflector 47 includes a facet total reflector lens 471 and two first adjustment bolts 472. The facet total reflector lens 471 is embedded in its inclined fixed base, and the angle of the facet total reflector can be adjusted by the first adjustment bolts 472. The facet total reflector 47 is installed directly above the specimen workbench 63 and at an angle of 45° to the horizontal plane. The facet total reflector 47 is fixed to the upper plate base 46 by bolts.

[0091] like Fig.13 As shown in FIG. 1 , the optical path of the three-directional moiré interference system is as follows: the light field passes through the double-hole blocking disk 43, and then refracts through the small total reflection mirror 44 and the reflector 45, and then irradiates the surface of the sample grating 14. The CCD image acquisition device 7 is placed opposite to the small plane reflective lens 471. The CCD image acquisition device 7 collects the fringe pattern formed by the light field interference on the sample through the small plane total reflection mirror 47, and transmits it to the computer.

[0092] The drilling machine 5 and the test piece experimental platform 6 are arranged longitudinally, and the drilling machine 5 includes: a drill bit 51, a first stepping motor 52, a second stepping motor 53 and two second adjusting bolts 54. The drill bit 51 is sleeved in a drill bit fixing sleeve on the drilling machine platform, and the drill bit is disassembled or tightened by two second adjusting bolts 54. The drilling machine 5 is connected to a computer via a data cable, and the computer can be input with relevant instructions to control the first stepping motor 52 to make the drill platform move forward and backward longitudinally along the slide rail, and the second stepping motor 53 can be controlled to make the drill bit 51 fixing seat move up and down. The rotation speed of the drill bit 51 can be controlled by inputting relevant instructions into the computer.

[0093] Furthermore, the special-shaped flexible universal fixture experimental platform 6 mainly includes a fixture floating pin 61, a floating pin locking switch 62, a jaw opening control handle 63, a screw 64, a workbench 65, and fine-tuning bolts 66 and 67. The fixture and the workbench 65 are fixed by screws 64. Fig.11 As shown, the fixture floating needle 61 is in a floating manner in the fixture seat, and the floating needle can be adjusted to a fixed position by the floating needle locking switch 62. Therefore, the floating needle 61 can adapt to any shape when it is unlocked, so that the present invention can measure the residual stress of expandable and non-expandable surfaces or composite material components with special complex geometric structures. The specimen 10 is placed in the jaws, and the jaws are controlled to shrink by the jaw opening control handle 63. As the left and right clamps gradually approach, the floating needle 61 adapts to the outer contour of the specimen 10 in a floating manner. The floating needle locking switch 62 is moved until the floating needle 61 is locked, and the specimen 10 is clamped. Then, the workbench 65 can be controlled to move longitudinally by the fine-tuning bolt 66, and the workbench 65 can be controlled to move horizontally by the fine-tuning bolt 67, so that the specimen grating 14 can be adjusted to the center of the incident light field.

[0094] The CCD image acquisition device 7 includes: a CCD industrial camera 71, a telescopic column 72, a fixed bracket 73, a limit screw 74, a magnetic base 75 and a fastening screw 76. The magnetic base 75 is turned on to fix it to the optical seismic isolation platform; the magnetic base 121 and the fixed bracket 73 are fastened and fitted by the fastening screw 76; the telescopic height of the telescopic column 72 can be controlled by the limit screw 74, so that the height of the CCD image acquisition device 71 can be adjusted. The CCD image acquisition device 7 is placed in front of the small plane total reflection mirror 47 and connected to the computer 1 through a data cable. The CCD image acquisition device 7 collects the stripe pattern formed on the specimen due to the light field interference through the small plane total reflection mirror 47 and transmits it to the computer 15.

[0095] Working principle: Fig.14 As shown, the laser 11 emits laser light, passes through the filter module 2 and the spatial filter module 3, and after filtering out the impurities at the edge of the light field, it is projected to the large plane total reflection mirror 41 to reflect the laser light to the collimating lens 42, so that the light field is transformed into a uniform collimated light field. The light field passes through the double-hole blocking optical disc 43, and then refracts through the small total reflection mirror 44 and the reflector 45, and then irradiates the surface of the specimen. The CCD image acquisition instrument 7 collects the stripe pattern formed on the specimen due to the light field intervention through the small plane total reflection mirror 47, and transmits it to the computer 15. By inputting relevant instructions to the computer 15, the drilling machine 5 is controlled to drill the specimen, and the residual stress field inside the specimen is released. After the drilling is completed, the stepping motors 52 and 53 are controlled to move the drill bit out of the light path. The CCD image acquisition instrument 7 collects the stripe picture of the surface of the specimen after drilling again, and transmits it to the computer 15 to analyze and compare the phase-shifted stripe pictures before and after drilling, and calculate the original residual stress of the specimen.

[0096] This embodiment aims to solve the limitations of the existing technology for measuring residual stress of curved composite materials. Through the special-shaped flexible universal fixture experimental platform, the outer contour of the test piece can be adaptively clamped. The device can measure carbon fiber composite components with different curvature surfaces or complex geometric structures, and has a wide range of applications. The interference fringe spacing can be controlled by changing the incident angle and frequency conversion to adapt to different measurement requirements and strain ranges, thereby improving the accuracy and flexibility of the measurement. A guide rail connection is provided in the optical path of the laser filter module and the spatial filter, and the optical axis is along the same track, which simplifies the fine-tuning control of the component spacing and the centering operation of the optical axis, thereby improving the test efficiency.

[0097] The phase-shift moiré interferometry experiment can obtain the displacement of any point on the edge of the hole, and then obtain the deformation of any point, thus solving the limitation of the traditional resistance strain rosette drilling method of taking the average strain value over a relatively large area and improving the measurement accuracy.

[0098] Different from the traditional moire interferometry method, this embodiment adopts the superposition state three-directional moire interferometry measurement technology with significant technical characteristics, and obtains independent displacement field image information in three directions at one time through the superposition state single-chip three-directional grating flower. It effectively solves the error caused by the movement of the specimen due to factors such as drilling when the orthogonal grating moire interferometry technology is combined with the drilling method to test the residual stress, and reduces the error caused by the plastic deformation caused by drilling.

[0099] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A residual stress measuring device for expandable and non-expandable curved composite material structures, characterized in that: It includes a laser generating module, a moiré interference module, a drilling module, a workpiece clamping module, an image acquisition module and a moiré interference module; The moiré interference module includes a collimating lens module, a double-aperture light-blocking plate, a total reflector and a reflector with adjustable inclination angle; the collimating lens module is used to receive laser light and separate the laser light into multiple directions; a total reflector and a reflector are respectively arranged in each splitting direction of the collimating lens module, so as to reflect the split light generated by the collimating lens module onto the workpiece; the double-aperture light-blocking plate is rotatably arranged between the collimating lens module and the total reflector, so as to select the split light in one direction to irradiate the workpiece; the inclination angle adjustment of the reflector is used to adjust the angle of the incident light on the workpiece.

2. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 1, characterized in that: The collimating lens module (42) comprises a collimating lens base (421), a base adjusting bolt (422) and a collimating lens (423); The collimating lens base (421) comprises a first fixing layer and a second fixing layer, the first fixing layer and the second fixing layer are connected via a base adjusting bolt (422), the adjusting bolt (422) is used to adjust the inclination angle of the first fixing layer, the first fixing layer is provided with a lens mounting hole matched with the collimating lens (423), the collimating lens (423) is mounted in the lens mounting hole; the second fixing layer is provided with a plurality of first-level light transmission holes which are centrally symmetrically distributed.

3. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 2, characterized in that: The double-hole light blocking plate (43) can be rotatably fixed on a side of the second fixed layer away from the first fixed layer, and the double-hole light blocking plate (43) is provided with two symmetrical secondary light-transmitting holes, which are located directly below the primary light-transmitting holes.

4. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 2, characterized in that: The collimating lens module (42) further comprises an upper plate base (46), and the upper plate base (46) is provided with third-level light-transmitting holes having the same number as the first-level light-transmitting holes; The number of the total reflection mirror and the reflector is the same as the number of the primary light-transmitting holes. The total reflection mirror and the reflector are both fixed on the upper plate base (46). The total reflection mirror is located directly below the primary light-transmitting hole and is used to emit the split light passing through the secondary light-transmitting hole to the reflector. The reflector is located directly above the tertiary light-transmitting hole. The workpiece clamping module is located on a side of the upper plate base (46) away from the reflector. The reflector is used to reflect the split light and irradiate it onto the workpiece through the tertiary light-transmitting hole.

5. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 4, characterized in that: The reflector comprises a fixing plate, an adjusting plate, a reflective lens (451) and a lens adjusting bolt (452); The fixing plate is fixed on the upper plate base (46); one end of the adjusting plate is provided with an inclined portion; the reflecting lens (451) is fixed on the inclined portion; the end of the adjusting plate opposite to the inclined portion is adjustably mounted on the fixing plate via a lens adjusting bolt (452); the lens adjusting bolt (452) is used to adjust the angle of incident light on the workpiece.

6. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 4, characterized in that: A framing total reflector is installed on one side of the upper plate base (46) away from the collimating lens module (42); the framing total reflector is located directly above the workpiece and is used to reflect stripes on the workpiece to the image acquisition module.

7. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 1, characterized in that: The laser generating module comprises a laser module (1), a filter module (2), a spatial filter module (3) and a spatial adjustment structure; The laser module (1), the filter module (2) and the spatial filter module (3) are fixed on the spatial adjustment structure; the filter module (2) and the spatial filter module (3) are used to filter stray light during laser propagation; and the spatial adjustment structure is used to adjust the heights of the laser module (1), the filter module (2) and the spatial filter module (3) respectively.

8. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 1, characterized in that: The workpiece clamping module includes a workbench (65) and two clamping arms. A plurality of clamp floating pins (61) arranged in an array are provided on the opposite side of the clamping arm for adapting to the shape of the workpiece. A floating pin locking switch (62) is also provided on the clamping arm for fixing the clamp floating pins (61). A spacing adjustment structure is installed on the workbench (65) for adjusting the spacing between the two clamping arms. The workbench (65) is used to adjust the position of the clamping arms on the horizontal plane.

9. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 1, characterized in that: The drilling module comprises a drill bit (51), a horizontal stepping motor (52) and a vertical stepping motor (53); The output shaft of the vertical stepper motor (53) is connected to the drill bit (51) for adjusting the longitudinal position of the drill bit (51), and the output shaft of the horizontal stepper motor (52) is connected to the horizontal stepper motor (52) for adjusting the lateral position of the drill bit (51).

10. The residual stress measuring device for expandable and non-expandable curved composite material structures according to claim 1, characterized in that: The image acquisition module comprises a CCD industrial camera (71) and a telescopic structure, wherein the CCD industrial camera (71) is fixed on the telescopic structure, and the telescopic structure is used to adjust the height of the CCD industrial camera (71). The CCD industrial camera (71) is used to acquire a stripe pattern on a workpiece, and the CCD industrial camera (71) is connected to a computer and uploads the acquired stripe pattern to the computer.

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